1. Field of the Invention
This invention relates to novel end-functionalized polylactones. More particularly, this invention relates to novel polylactone aromatic esters and their use in fuel compositions to prevent and control engine deposits.
2. Description of the Related Art
It is well known that automobile engines tend to form deposits on the surface of engine components, such as carburetor ports, throttle bodies, fuel injectors, intake ports and intake valves, due to the oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile's fuel consumption and production of exhaust pollutants. Therefore, the development of effective fuel detergents or "deposit control" additives to prevent or control such deposits is of considerable importance and numerous such materials are known in the art.
For example, polyether amine fuel additives are well known in the art for the prevention and control of engine deposits. These polyether additives have a poly(oxyalkylene) "backbone", i.e., the polyether portion of the molecule consists of repeating oxyalkylene units. U.S. Pat. No. 4,191,537, issued Mar. 4, 1980 to R. A. Lewis et al., for example, discloses a fuel composition comprising a major portion of hydrocarbons boiling in the gasoline range and from 30 to 2,000 ppm of a hydrocarbyl poly(oxyalkylene) aminocarbamate having a molecular weight from about 600 to 10,000, and at least one basic nitrogen atom. The hydrocarbyl poly(oxyalkylene) moiety is composed of oxyalkylene units having from 2 to 5 carbon atoms in each oxyalkylene unit. These fuel compositions are taught to maintain the cleanliness of intake systems without contributing to combustion chamber deposits.
Poly(vinyl ether) amine fuel additives are also known in the art. For example, U.S. Pat. No. 5,306,314 discloses poly(vinyl ether) aminocarbamate fuel additives having a vinly ether polymer backbone consisting of repeating vinyl ether units. These compounds are taught to be useful in fuel compositions to prevent and control engine deposits.
Polylactone polymer compositions have also been reported in the art. For example, U.S. Pat. No. 5,028,667 to McLain et al., discloses a process for the ring-opening polymerization of lactones using as catalysts compounds of yttrium and the rare earth metals. This patent further teaches that the resulting polylactone polymers are useful as biodegradable polymers for medical uses and as flexible films for packaging.
P. Dubois et al., in Macromolecules, 1992, Volume 25, Pages 2614-2618, describe the ring-opening polymerization of caprolactone initiated by primary amines and trialkylaluminum. The resulting polycaprolactone is taught to be useful in the biomedical field due to its high permeability, lack of toxicity for living organisms, biodegradability and capacity to be blended with various commercial polymers over a wide composition range. D. Tian et al., in Macromolecules, 1994, Volume 27, Pages 4134-4144, describe star-branched polycaprolactone polymers having primary amine end groups. These polymers are prepared by the ring-opening polymerization of caprolactone with aluminum alkoxides and a trimesic acid trichloride termination agent.
U.S. Pat. No. 4,820,432 to Lundberg et al. discloses poly (C.sub.5 to C.sub.9 lactone) modified Mannich base adducts which are prepared by reacting a C.sub.5 to C.sub.9 lactone, an amine, an aldehyde, an N-hydroxyarylamine, and a hydrocarbyl substituted C.sub.4 to C.sub.10 monounsaturated dicarboxylic acid producing material, such as a polyisobutenyl succinic anhydride. These modified Mannich base adducts may be prepared, for example, by first reacting an N-hydroxyarylamine with a hydrocarbyl substituted dicarboxylic acid producing material to form an N-hydroxyaryl hydrocarbyl substituted imide, which is subsequently reacted with an aldehyde and an amine to form an intermediate Mannich base adduct having an amino functional group capable of initiating lactone ring opening polymerization, and then reacting the intermediate Mannich base adduct with a C.sub.5 to C.sub.9 lactone. This patent further teaches that the resulting poly (C.sub.5 to C.sub.9 lactone) modified Mannich base adduct is useful as an oil soluble dispersant additive for fuel and lubricating oil compositions.
It has now been discovered that certain polylactone aromatic esters provide excellent control of engine deposits, especially intake valve deposits, when employed as fuel additives in fuel compositions.